Never allow your bare feet to kick, shuffle, or drag along the ground. It is lateral movement that produces the great majority of risk of cutting from any sharp surfaces.
Stop if you want to take a good look at something off the path. When your bare feet are in motion, focus most often on the part of the path two to three paces in front. This practice will become very important when you are hiking on stony or otherwise uneven terrain. you should definitely begin it on your first day of barefoot hiking even if you are on the mildest of trails. being a matter of sensory coordination, much like catching a ball, it is a skill that develops mostly on an unconscious level, but you can consciously help it along help it along by contemplating the fact that you are learning to coordinate two of your senses: the sight of your eyes and the newly discovered tactile sensitivity of your bare soles.
This does not mean that you should walk in tiptoe (although there are situations in which that is very effective). Rather, it means that you should try, within comfortable limits, to keep more weight on the forward part of your foot, and to keep it there for a longer time during the course of each step, than might previously been your habit. To understand this, let's examine a typical pair of bare feet. The skin of the heel is usually thick and hard compared with the rest of the foot. Between this quarter inch of leather and the bone of the heel is a cushion of very tough and resilient tissue. Although this is an efficient shock absorber (especially when you consider that it is no more than a half inch thick), it definitely has it's limitations.
Moving on to the middle of the foot, you will find the cannon bones or metatarsals. These form part of a shock absorption system that is far more effective than the cushion of the heel.
Now examine the ball of the foot. Supple and yielding, yet tough and resilient, this is both the most sensitive part of the sole, and the part where nature intended that most of the weight of the body (in motion) should be borne. Notice how broad this part of the foot is and how much larger an area it present to the ground than the heel. Feel how flexible it is, how not only each of the toes, but each of the metatarsals behind the toes, can move up and down independently to mold to the contour of the earth. Feel the flexibility and strength of all the joints that allow the front part of the foot to absorb shock so much better than the heel.
You must never forget you are going barefoot, you must always devote a part of your attention (or consciousness) to your bare soles. The tread of a barefoot hiker should always be soft and light, sometimes it must be wary and tentative. Be careful and deliberate as you rotate and maneuver your feet around obstacles. You should be ready to retract a step if you don't like the feeling of what you are stepping on. Occasionally, you will step on something pointy even though you looked carefully before placing your foot. It may be too late to retract the step. The trick here is to quickly shift the weight onto other parts of your foot (heel --> ball, and so on). As you become more conditioned, this will be less of a problem since your soles will be thicker and the (now stronger and more agile) muscles and tendons of your feet will be more adapted to rapid re-configuration. Feet in this kind of condition feel really good !! (barefoot or not).
Much of the above material has been adapted from:
"The Barefoot Hiker" by Richard Frazine.
Ten Speen Press. ISBN 0-89815-525-8
Beginning Barefoot Hiking
Barefoot Hiking: General